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Environmental Science & Technology 04/2013; · 4.80 Impact Factor
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ABSTRACT: Effects of pH, alkalinity and conductivity on the adsorption of soluble reactive phosphorus (SRP) onto lanthanum (La) modified bentonite clay (Phoslock(®)) were investigated in laboratory experiments using eight different types of filtered water representing freshwater with low and normal alkalinity and brackish water with high alkalinity. Different dose ratios (0-200; w/w) of Phoslock(®):P were applied to determine the maximum P binding capacity of Phoslock(®) at SRP concentrations typical of those of sediment pore water. The 100:1 Phoslock(®:)P dose ratio, recommended by the manufacturer, was tested with 12 days exposure time and generally found to be insufficient at binding whole target SRP pool. The ratio performed best in the soft water from Danish Lake Hampen and less good in the hard water from Danish Lake Langesø and in brackish water. The explanation may be an observed negative relationship between alkalinity and the SRP binding capacity of Phoslock(®). A comparative study of Lake Hampen and Lake Langesø suggested that the recorded differences in P adsorption between the two lakes could be attributed to a more pronounced dispersion of Phoslock(®) in the soft water of Lake Hampen, leading to higher fractions of dissolved (<0.2 μm) La and of La in fine particles. In the same two lakes, pH affected the SRP binding of Phoslock(®) negatively at a pH level above 8.1, the effect being reversible, however. The negative pH effect was most significant in hard water Lake Langesø, most likely because of higher [Formula: see text] concentrations.
Water Research 03/2013; · 4.86 Impact Factor
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ABSTRACT: The possible pH dependent dissolution of aluminum hydroxides (Al(OH)(3)) from lake sediments was studied in six lakes previously treated with Al to bind excess phosphorus (P). Surface sediment was suspended for 2 h in lake water of pH 7.5, 8.5, or 9.5 with resulting stepwise increments in dissolved Al observed in all lakes. The amount of dissolved Al increased proportional to the sediment content of Al(OH)(3) as quantified by a sequential extraction technique. Up to 24% of the sediment Al(OH)(3) could dissolve within 2 h at pH 9.5 and a portion of sediment P was dissolved concomitantly. Lowering pH to 7 caused 30-100% of the dissolved Al to precipitate again after 24 h. Re-precipitation of mobilized P varied from 50% to more than 100%. A test with untreated sediment showed the same proportionality which means that also indigenous Al(OH)(3) can dissolve frequently in lakes with high pH water. Release rates of dissolved Al from intact sediment cores at the same three pH values was measured in three of the lakes, and showed increased Al release rates at pH 8.5 in one of the lakes and 9.5 in two of the lakes. Our study demonstrates a risk of dissolution of sediment Al(OH)(3) to form aluminate in shallow lakes, where resuspension and high pH in the water occurs frequently. In the worst case dissolved Al may reach toxic levels in lakes treated by Al but also the concomitant release of P and the possible loss of dissolved Al to downstream ecosystems are negative effects that may occur already at more modest dissolution of Al(OH)(3) and Al-bound P.
Water Research 12/2012; · 4.86 Impact Factor
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ABSTRACT: Phosphorus (P) binding groups were identified in phytoplankton, settling particles, and sediment profiles by 31P NMR spectroscopy from the Swedish mesotrophic Lake Erken. The 31P NMR analysis revealed that polyphosphates and pyrophosphates were abundant in the water column, but rapidly mineralized
in the sediment. Orthophosphate monoesters and teichoic acids degraded more slowly than DNA-P, polyphosphates, and P lipids.
Humic acids and organic acids from phytoplankton were precipitated from the NaOH extract by acidification and identified by
31P NMR spectroscopy. The precipitated P was significantly more recalcitrant than the P compound groups remaining in solution,
but does not constitute a major sink of P as it did not reach a stable concentration with depth, which indicates that it may
eventually be degraded. Since P also precipitated from phytoplankton, the origin of humic-P can not be related solely to allochthonous
P.
Biogeochemistry 04/2012; 82(1):15-28. · 3.07 Impact Factor
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ABSTRACT: Solution (31)phosphorus NMR spectroscopy and sequential fractionation were used to follow diagenetic changes in phosphorus forms during decomposition of settling seston in Lake Nordborg, a shallow eutrophic lake in Denmark. In a decomposition experiment, seston released >60% of their total phosphorus during ~50 days incubation, although seston collected during summer contained more phosphorus and released it over a longer period compared to seston collected during spring. Seston decomposition increased concentrations of potentially bioavailable polyphosphate and phosphodiesters, but also promoted the formation of refractory phosphorus forms that might be buried permanently in the sediment. Combining these results with in situ measurements of phosphorus concentrations in lake water and sediment traps revealed that the release from settling seston plays only a minor role in the accumulation of phosphorus in the hypolimnion of Lake Nordborg.
Journal of Environmental Monitoring 03/2012; 14(3):1098-106. · 1.99 Impact Factor
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ABSTRACT: Orthophosphate monoesters often constitute a significant fraction of total phosphorus in lake sediments. The knowledge on the specific composition and recalcitrance of these compounds is however limited. The main aim was therefore to identify and quantify specific orthophosphate monoesters in sediment from 15 Danish lakes by solution (31)P NMR spectroscopy. The four most quantitatively important orthophosphate monoesters were myo-inositol hexakisphosphate (myo-IP(6)), scyllo-inositol hexakisphosphate (scyllo-IP(6)) α-glycerophosphate (α-GP) and β-glycerophosphate (β-GP). The compounds were identified in 9, 4, 8 and in all 15 lakes, respectively. In total these four components made up 46-100% of the orthophosphate monoester pool. The glycerophosphates (GPs) are most likely degradation products of phospholipids, created as an artifact by the alkaline extraction procedure used for (31)P NMR spectroscopy, while the inositol hexakisphosphates (IPs) are naturally occurring compounds. There was a significant positive correlation between myo-IP(6) and total aluminium in the sediment and a negative correlation between myo-IP(6) and lake water pH, suggesting that myo-IP(6) is stabilized in the sediment by adsorption at slightly acidic or neutral conditions. In three lakes, the depth distribution of the orthophosphate monoesters was investigated. The content of scyllo-IP(6) and myo-IP(6) was constant with sediment depth in two of the lakes while the content of myo-IP(6) decreased with depth in one of the lakes. In all cases the IPs seem to be preserved with sediment depth to a higher extent than the orthophosphate diesters and especially the GPs suggesting that IPs can be a sink for phosphorus in the lake ecosystem or at least delay P-recycling for years.
Journal of Environmental Monitoring 06/2011; 13(8):2328-34. · 1.99 Impact Factor
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ABSTRACT: Loading, retention, and in-lake cycling of phosphorus (P), nitrogen, silica, and dissolved organic carbon (DOC) were studied 1 year before and 3 years after P-inactivation by aluminum (Al) hydroxide in Danish Lake Nordborg in 2006. Simultaneously, external P loading was reduced by 40% via establishment of precipitation ponds in two inlets. After Al treatment, the internal P loading (sediment P release) during summer declined 90%–94%, owing to adsorption to aluminum hydroxide. Also, silicate regeneration from the sediment was reduced by 69%–76%, and sediment oxygen uptake as well as ammonium release declined markedly. Consequently, lake water total P, dissolved inorganic P, silicate, and DOC decreased by 73%, 97%, 87%, and 46%, respectively. The Secchi depth increased in the summer period during the first post-treatment year, but declined afterwards to pre-treatment levels, even though the mean lake-water total P concentration during summer was reduced from 240 µg·L–1 before treatment to 26–65 µg·L–1 in the first three post-treatment years. We conclude that a further reduction in external P loading is needed to obtain the full effect of the Al treatment in Lake Nordborg.
Canadian Journal of Fisheries and Aquatic Sciences 05/2011; 68(5):842-856. · 2.21 Impact Factor
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ABSTRACT: Laboratory experiments with sediments from three shallow Danish lakes were conducted to evaluate the effects of chemical lake restoration products during resuspension. Phosphorus (P) removal, sediment stability, sediment consolidation and color reduction were studied over time. The investigated products were aluminum (Al), Phoslock (a commercial bentonite product coated with lanthanum) and a combination of Al covered with bentonite (Al/Ben). All treatments effectively reduced the P concentration in the water. However, the treatments containing Al reduced the P concentration immediately after resuspension, whereas Phoslock required several days after resuspension to reduce the P concentration. Especially Phoslock, but also Al/Ben, increased the sediment stability threshold by 265% and 101%, respectively, whereas Al had no stabilizing effect. The fresh Al floc was resuspended 5x easier than untreated sediment. The largest consolidation of the sediment occurred with addition of Phoslock, followed by Al/Ben, while Al alone had no effect. Enhanced consolidation may be of importance for macrophyte colonisation of organic sediment. Phoslock improved the light climate moderately by removing color, whereas Al was very effective in removing color. Ben/Al showed intermediate effects on color reduction. These findings are important when decisions are made on restoration method for a specific lake, which may be more or less wind exposed.
Environmental Science and Technology 02/2010; 44(3):985-91. · 5.23 Impact Factor
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ABSTRACT: Little information exists on nonreactive phosphorus (nrP) in the water column, because the concentration is much lower than that in the sediment. Here we present a novel method for up-concentration and identification of nrP in lake water: nrP is precipitated with poly aluminum chloride and the precipitate is subsequently recovered and dissolved by NaOH. Additional up-concentration by rotary evaporation increases P concentrations up to 5500 times. Furthermore, there is only a low up-concentration of paramagnetic metals. The method is sensitive and easy to use. Bottom water from five Danish lakes was sampled in autumn 2008 and in four of the five lakes orthophosphate monoesters constituted the largest fraction of nrP (50-86%), whereas DNA-P was the largest fraction in the fifth lake (67%). The pyro-P/poly-P concentration varied between 0 and 33% of nrP in the lakes. Thus, most of the P compounds usually found in lake sediments were also found in the bottom water of these lakes.
Environmental Science and Technology 08/2009; 43(14):5391-7. · 5.23 Impact Factor
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ABSTRACT: Phosphorus (P) composition in alkaline sediment extracts from three Swedish oligotrophic mountain lakes was investigated using 31P-NMR spectroscopy. Surface sediments from one natural lake and two mature reservoirs, one of which has received nutrient additions over the last 3 years, were compared with respect to biogenic P composition. The results show significant differences in the occurrence of labile and biogenic P species in the sediments of the different systems. The P compound groups that varied most between these three systems were pyrophosphate and polyphosphates, compound groups known to play an important role in sediment P recycling. The content of these compound groups was lowest in the reservoirs and may indicate a coupling between anthropogenic disturbances (i.e., impoundment) to a water system and the availability of labile P species in the sediment. A statistical study was also conducted to determine the accuracy and reliability of using 31P-NMR spectroscopy for quantification of sediment P forms.
Water Research 01/2007; 40(20):3705-12. · 4.86 Impact Factor
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ABSTRACT: Phosphorus (P) compounds in three different lake surface sediments were extracted by sequential P extraction and identified by P-31 nuclear magnetic resonance (P-31 NMR) spectroscopy. The extraction procedure primarily discriminates between inorganic P-binding sites but most extraction steps also contained P not reacting (nrP) with the molybdenum complex during P analyses. In all three lakes, the nrP dominated in the NaOH extracts. Nonreactive P from the dystrophic lake was dominated by potentially recalcitrant P groups such as orthophosphate monoesters, while the nrP in the two more productive lakes also contained polyphosphates, pyrophosphate, and organic P groups such as P lipids and DNA-P that may be important in remineralization and recycling to the water column. In addition, polyphosphates showed substantial dynamics in settling seston. The Humic-P pools (P associated with humic acids) showed strong signals of orthophosphate monoesters in all three lakes, which supported the assumption that P-containing humic compounds are indeed recovered in this fraction, although other organic P forms are also present. Thus, in addition to expanding the understanding of which organic P forms that are present in lake sediments, the P-31 NMR technique also demonstrated that the chemical extraction procedure may provide some quantification of recalcitrant versus labile organic P forms.
Canadian Journal of Fisheries and Aquatic Sciences 08/2006; 63(8):1686-1699. · 2.21 Impact Factor
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ABSTRACT: The effects of aluminum (Al) treatment on sediment composition of carbon (C), nitrogen (N) and phosphorus (P) were investigated in sediment representing pre- and post-treatment years in the Danish Lake Sønderby. 31P NMR spectroscopy analysis of EDTA-NaOH extracts revealed six functional P groups. Direct effects of the Al treatment were reflected in the orthophosphate profile revealing increased amounts of Al-P in the sediment layers representing the post-treatment period, as well as changes in organic P groups due to precipitation of phytoplankton and bacteria at the time of Al addition. Furthermore, changes in phytoplankton community structure and lowered production due to the Al treatment resulted in decreased concentrations of sediment organic P groups and total C. Exponential regressions were used to describe the diagenesis of C, N, and P in the sediment. From these regressions, half-life degradation times and C, N, and P burial rates were determined.
Water Research 03/2006; 40(4):647-54. · 4.86 Impact Factor
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ABSTRACT: In the sediment of the shallow, hypertrophic Lake Sønderby, Denmark, potentially mobile phosphorus (Pmobile) was determined by a sequential extraction technique as the sum of porewater P, iron-bound P, and nonreactive P (i.e., polyphosphates and organic P). A good agreement was observed between loss rates of Pmobile in the top 10 cm of the sediment from winter to summer, P release rates measured in undisturbed sediment cores, and rates of P accumulation in the lake water from winter to summer (22, 32, and 30 mg of P m(-2) day(-1), respectively). This suggests that the operationally defined Pmobile was the sediment P fraction responsible for the internal loading in the lake. In autumn 2001, 11 mg of aluminum (Al) L(-1), equivalent to 31 g of Al m(-2), was added to the lake water. This dosage represented a 4:1 molar ratio between Al and Pmobile. The Al treatment significantly decreased lake water P, and P precipitated from the lake water was recovered as Al-bound P in the sediment after the treatment. Internal P loading was reduced by 93% in the two posttreatment years, relative to 2001. Accordingly, average summer concentrations of total P in lake water declined from 1.28 (SE = 0.17) and 1.3 (SE = 0.14) mg L(-1) in the two pretreatment years to 0.09 (SE = 0.01) and 0.13 (SE = 0.01) mg L(-1) in the posttreatment years. pH levels remained unchanged relative to pretreatment levels, while the total alkalinity was reduced from 3.2 (SE = 0.04) to 2.7 (SE = 0.03) mequiv L(-1).
Environmental Science and Technology 07/2005; 39(11):4134-40. · 5.23 Impact Factor
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ABSTRACT: Internal phosphorus (P) loading in shallow lakes may delay recovery from previous high external loading for decades. In Lake Snderby (8 ha, mean depth 2.8m), Fyn County, Denmark, this is especially true because there is no run-off of lake water during summer when high lake water P concentrations prevail. External P-loading was reduced in 1983 but still in 2001 total P reached 1.5mg l–1 during summer. In the present study, we determined the size of the potential mobile P-pool in the sediment by use of a sequential extraction procedure. The potentially mobile P-pool (PMobile): Loosely adsorbed inorganic o-P (PWater), iron-bound o-P (PBD), and labile organic P (Org-PLabile) made up 14.6 gm–2 and constituted 40% of the Tot-P in the upper 10cm sediment. Then, we tested if molar binding ratios of 4:1 or 8:1 between aluminum (Al) and potential mobile P could reduce sediment P-release at suboxic conditions. An Al:P ratio of 4:1 was enough (pn=5) to trap all P in the sediment during a 39 days experiment with undisturbed sediment cores. This dosage was then tested in enclosures in the lake during a 30 days summer experiment with 3 replicate enclosures (1.1m2, 2.1m high) for each of the 2 treatments (Al addition, and control). o-P and Tot-P dropped from 1.28mg l–1 to –1, respectively, in the Al treated enclosures but remained high in both control enclosures and in the lake water. Secchi depth increased from 0.8m to the bottom upon Al treatment but declined to around 1.5m after 4 days. By the end of the enclosure experiment, sediment analyses showed increased fractions of P\to NaOH in the surface sediment of Al treated enclosures. We conclude that Al addition was able to combat internal P-loading in the shallow lake when added in a molar ratio of 4:1 relative to the mobile P-pool in sediment and lake water. Meanwhile, temporary suppression of Daphnia grazing may be expected upon Al addition.
Hydrobiologia 10/2003; 506-509(1):781-787. · 1.78 Impact Factor
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ABSTRACT: The effects of oxygen, aluminum, iron and nitrate additions on phosphate release from the sediment were evaluated in the softwater Lake Vedsted, Denmark, by a 34-day experiment with undisturbed sediment cores. Six treatments were applied: (1) Control - O2 (0–20% saturation), (2) O2 (100% saturation) (3) Al3+ – O2, (4) Fe3+ + O2, (5) Fe3+ – O2, and (6) NO3
– – O2. Al2(SO4)3*18 H2O and FeCl3*4H2O were added in amounts that theoretically should immobilize the exchangeable P-pool in the top 5 cm of the sediment, while sodium nitrate concentrations were increased to 5 mg N l–1. The four treatments with metals or NO3
– reduced the P efflux from the sediment significantly as compared to the suboxic control treatment. Mean accumulated P-release rates for suboxic treatments with Al3+, Fe3+, and NO3
– were: –0.27 mmol m–2 (st. dev = 0.02 mmol m–2, N = 5), 0.58 mmol m–2 (st. dev = 0.30 mmol m–2, N = 5) and 1.40 mmol m–2 (st. dev = 0.14 mmol m–2, N = 5), respectively. The oxic treatment with Fe3+ had a P efflux of 0.36 mmol m–2 (st. dev = 0.08 mmol m–2, N = 5). The two highest P-release rates were observed in the control treatment and the treatment with O2 (14.50 mmol m–2 (st. dev = 3.90 mmol m–2, N = 5) and 2.31 mmol m–2 (st. dev = 0.80 mmol m–2, N = 5), respectively). In order to identify changes in the P and Fe binding sites in the sediment as caused by the treatments, a sequential P extraction procedure was applied on the sediment before and after the efflux experiment. Addition of O2, Fe3+ and NO3
– to the sediment increased the amounts of oxidized Fe3+ and PBD. Al3+ addition resulted in a lower fraction of PBD but a correspondingly higher fraction of Al-bound P. Addition of Al3+ decreased the Fe-efflux from the suboxic sediment as well as the amount of oxidized Fe3+ in the sediment. This questions the use of Al compounds that contain sulfate because of the possible formation of FeS, which will restrict upward migration of Fe2+ and the formation of new Fe-oxides in the surface sediment. Instead, we suggest the use of AlCl3 for lake restoration purposes.
Hydrobiologia 01/2003; 492(1):139-149. · 1.78 Impact Factor
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ABSTRACT: The influence of pre-extractant, extractant, and post-extractant on total extracted amounts of P and organic P compound groups measured with 31P nuclear magnetic resonance (31P-NMR) in lacustrine sediment was examined. The main extractants investigated were sodium hydroxide (NaOH) and sodium hydroxide ethylenediaminetetraacetic acid (NaOH-EDTA) with bicarbonate buffered dithionite (BD) or EDTA as pre-extractants. Post extractions were conducted using either NaOH or NaOH-EDTA, depending on the main extractant. Results showed that the most efficient combination of extractants for total P yield was NaOH with EDTA as pre-extractant, yielding almost 50% more than the second best procedure. The P compound groups varying the most between the different extraction procedures were polyphosphates and pyrophosphates. NaOH with BD as pre-extractant was the most efficient combination for these compound groups.
Journal of Environmental Quality 36(3):892-8. · 2.32 Impact Factor
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ABSTRACT: To avoid eutrophication of receiving waters, effective methods to remove P in urban and agricultural runoff are needed. Crushed concrete may be an effective filter material to remove dissolved and particulate P. Five types of crushed concrete were tested in the laboratory to evaluate the retention capacity of dissolved P. All types removed P very effectively (5.1-19.6 g P kg(-1) concrete), while the possible release of bound P varied between 0.4 and 4.6%. The retention rate was positively related to a decreasing concrete grain size due to an increasing surface area for binding. The P retention was also related to a marked increase in pH (up to pH 12), and the highest retention was observed when pH was high. Under these circumstances, column experiments showed outlet P concentrations <0.0075 mg P L(-1). Furthermore, experiments revealed that release of heavy metals is of no importance for the treated water. We demonstrate that crushed concrete can be an effective tool to remove P in urban and agricultural runoff as filter material in sedimentation/infiltration ponds provided that pH in the treated water is neutralized or the water is diluted before outlet to avoid undesired effects caused by the high pH.
Journal of Environmental Quality 41(3):647-53. · 2.32 Impact Factor
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ABSTRACT: The composition and abundance of phosphorus extracted by NaOH–ethylenediaminetetraacetic acid from anoxic Northwest Baltic Sea sediment was characterized and quantified using solution 31 P nuclear magnetic resonance. Extracts from sediment depths down to 55 cm, representing 85 yr of deposition, contained 18.5 g m 22 orthophosphate. Orthophosphate monoesters, teichoic acid P, microbial P lipids, DNA P, and pyrophosphate corresponded to 6.7, 0.3, 1.1, 3.0, and 0.03 g P m 22 , respectively. The degradability of these compound groups was estimated by their decline in concentration with sediment depth. Pyrophosphate had the shortest half-life (3 yr), followed by microbial P lipids with a half-life of 5 yr, DNA P (8 yr), and orthophosphate monoesters (16 yr). No decline in concentration with sediment depth was observed for orthophosphate or teichoic acid P. Eutrophication is a major environmental problem in the Baltic Sea (e.g., Rö nnberg and Bonsdorff 2004), but there is a lack of consensus whether nitrogen (N) (Blomqvist et al. 2004) or phosphorus (P) (Hecky 1998) is limiting overall primary production in the Baltic proper. Contrary to N, P has no gaseous phase, meaning that the supply of P for primary production is dependent on external sources as well as internal recycling. Until the mid-1980s, external P loading to the Baltic Sea had increased eightfold compared with a century ago (Larsson et al. 1985). Although total riverine input of P to the Baltic Sea showed a slight downward tendency during the 1990s (Stå hlnacke et al. 1999), total external loading into the Baltic Sea has been fairly constant over the last decades (HELCOM 2005). In spite of the stabilized external loading, water column P concentrations in the Baltic Sea show an increasing tendency, most likely due to internal P loading (Emeis et al. 2000). The amount and forms of organic sediment P that contribute to the internal loading process are basically not known, and such information would be of great importance for prediction of the future status of Baltic Sea water quality. Most of the knowledge about P in sediment concerns inorganic P forms obtained from various sequential extrac-tion procedures, but more specific information about the chemical forms of organic P is lacking, in spite of the quantitative importance of these compounds (Turner et al. 2005). 31 P nuclear magnetic resonance (31 P NMR) spectros-copy is a suitable method for assessing the general composition of P in a variety of matrixes since it, by using the resonance yielded by the P atom when it is placed in a strong magnetic field, can indicate what ligands are attached to the P atom. The method can indicate whether there is, for example, orthophosphate, pyrophosphate, or polyphosphate in the sample, or whether some of the P is situated in organic forms such as orthophosphate monoe-sters, diesters, or phosphonates. 31 P NMR can also be used to investigate possible changes in the P composition, thus making it possible to assess trends of P compounds in terms of degradation and mineralization (e.g., Ahlgren et al. 2005). 31 P NMR spectroscopy has been used by a number of researchers since the 1980s to identify organic P com-pounds in environmental samples, including sediments 1 Corresponding author (emil.rydin@ebc.uu.se).
